A. Field of the Invention
The present invention relates to new and improved systems for utilizing solar energy to heat domestic water systems and to heat and cool residential and commercial buildings.
B. Description of the Prior Art
Solar energy is one of the few safe, inexhaustable, and pollution free energy resources presently available. As technology and present fuel prices increase, the utilization of solar energy will become even more economically feasible. In view of this and the fact that the utilization of solar energy is particularly applicable to the heating and cooling of commercial and residential buildings and to the heating of domestic water, heat from solar radiation has been used in various forms for many years.
However, use of the sun's energy suffers from several disadvantages. For example, in solar heating 100% standby heat is required. This is necessary to compensate for prolonged periods when solar energy is not available. These periods include cloudy and/or rainy days and winter evenings.
In addition, the time varying nature of a solar system requires substantial standby heat storage. Storage is necessary to accumulate quantities of heat during the times when solar energy is available, i.e., during the day when requirements are low, in order to provide sufficient supply during peak heat demand periods, usually occurring after sundown. This can greatly increase the cost of installing and utilizing a solar energy system, since in addition to equipment for 100% standby storage, fluid must be stored at prolonged periods of time and must be maintained at a high temperature throughout these periods.
In a system utilizing fluids as heat storage media, to achieve sufficient heat content for heating over prolonged periods of time with equipment of reasonable cost and size stored fluid must be elevated to a substantial temperature. However, elevating the temperature above the fluid's atmospheric boiling point requires operation at high pressure and results in production of steam substantially reducing the utility of the stored fluid. Therefore, prior art solar heat systems have utilized sub-boiling operation. A solar system employed for heating that only utilizes low pressure, and, thus, low temperature fluid is disclosed on pages 8-14 in a paper presented to the American Society of Civil Engineers Annual and National Engineering Convention in Kansas City, Missouri on Oct. 25, 1974. This paper was written by Craig Lentz of Arthur D. Little, Inc., Cambridge, Massachusetts. However, as indicated above, systems of this type require extremely large storage tanks to provide adequate capacity.